In accordance with functionality increase and downsizing of semiconductor packages widely used in electronic devices, communication devices, personal computers and the like, high integration and high-density packaging of each component for semiconductor packages have been increasingly accelerated in recent years. As a result, a difference in the coefficient of thermal expansion between a semiconductor device and a printed circuit board for a semiconductor plastic package disadvantageously causes warp of the semiconductor plastic package, and there have been various countermeasures against this problem.
One of the countermeasures is reduction of the thermal expansion of an insulating layer for use in a printed circuit board. In this countermeasure, the warp is suppressed by setting the coefficient of thermal expansion of a printed circuit board to be close to the coefficient of thermal expansion of a semiconductor device, and this method is now actively employed (see, for example, Patent Literatures 1 to 3).
In addition to the reduction of the thermal expansion of a printed circuit board, as a method for suppressing the warp of a semiconductor plastic package, increase of rigidity (rigidity increase) of a laminate and increase of a glass transition temperature (Tg increase) of a laminate are now being examined (see, for example, Patent Literatures 4 and 5).